To get to the Google account settings, click on “gear” and “settings” in your web browser. Now you can delete Yahoo e-mail from your Google account.
How do I remove my Yahoo account from Gmail?
Go to your Google account and select the gear icon. Then choose the “Settings” (gear icon) section. Then click the “Accounts and Import” tab. You will see Yahoo e-mail at the bottom of the page. Click the “delete” button.